Antiknock tetramethyl lead concentrate

ABSTRACT

An antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger and hydrocarbon liquid is disclosed.

United States Patent Richardson et al.

[ July4, 1972 [54] ANTIKNOCK TETRAMETHYL LEAD CONCENTRATE Wallace L. Richardson, Lafayette; George ,I. Kautsky, El Ccrrilo; Maurice R. Barusch, Richmond, all of Calif.

[73] Assignee: Chevron Research Company [22] Filed: July 11,1960

[2]] Appl. No.: 41,780

[72] Inventors:

[52] US. Cl. ..260/437 S, 44/69, 252/386 [51] Int. Cl. ..C07f 7/24 [58] Field of Search ..252/386; 44/69; 260/437, 437 S;

[56] References Cited UNITED STATES PATENTS 2,004,160 6/1935 Downing et al ..260/437 Chem. Reviews (Amer. Chem. Soc.) Feb. I954, Vol. 54, No. l

Organolead Compounds by Leeper et al., pages 105- 107 Primary Examiner-Tobias E. Levow Assistant ExaminerH. M. S. Sneed Attorney-A. L. Snow, F. E. Johnston and John Stoner, Jr.

[5 7] ABSTRACT An antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger and hydrocarbon liquid is disclosed.

3 Claimgfio Drawings ANTIKNOCK TE'I'RAMETHYL LEAD CONCENTRA'I'E This invention relates to an improved antiknock concentrate for gasoline compositions. More particularly, the invention is concerned with superior new tetramethyl lead antiknock concentrate having improved explosibility characteristics which afford a greater degree of safety in gasoline blending operations.

Tetraethyl lead has been commonly used as an antiknock material for raising the octane number of gasoline compositions. However, the search for improved gasoline compositions of higher octane number for use in high compression engines has resulted in the important discovery that tetramethyl lead is surprisingly more efiective as an antiknock agent than tetraethyl lead in certain highly aromatic gasolines. This is particularly so on the road, where automobile engine performance is measured by the motorist.

Although tetramethyl lead is superior to tetraethyl lead in certain gasoline compositions, as an antiknock, it has an unexpected drawback due to the fact that it is found to be more explosive and sensitive to detonation by shock than tetraethyl lead. This constitutes a serious safety problem in actual operations. For practical purposes, it is customary to transport antiknock materials in either the form of the compounds as such, or in the form of concentrates which commonly contain scavengers of the halohydrocarbon type, in order to keep down shipping costs and other handling expenses. In such forms the extra explosibility and shock sensitivity of tetramethyl lead make it more hazardous to handle and thus tend to offset the practical advantages of the aforementioned octane number improvement.

It has now been found that tetramethyl lead antiknock compositions having improved explosibility characteristics are.

provided in the form of a concentrate comprising tetramethyl lead and hydrocarbon liquid, the hydrocarbon liquid content of the concentrate being in the range from about to about 150 percent by weight of the tetramethyl lead.

For present practical purposes the compositions of this in vention have their preferred embodiment as an antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger and hydrocarbon liquid as mentioned above.

In the antiknock concentrates according to this invention, the extra explosibility of tetramethyl lead, compared to conventional tetraethyl lead, is essentially eliminated. Such concentrates are as safe to handle as conventional tetraethyl lead. They are conveniently transported without increased shipping costs which would detract from the economic benefits of improved octane number performance provided by tetramethyl lead in gasoline compositions.

The hydrocarbon component of the concentrate according to the invention is normally liquid under ordinary atmospheric pressures and temperatures. Suitable hydrocarbons include straight-chain parafiins, branched-chain paraffins, olefins, aromatics and naphthenes such as n-octane, n-nonane, ndecane, Z-methylheptane, 2,2,3-trimethylpentane, 2-hexene, diisobutylene, benzene, toluene, xylene, dimethylcyclopentane and cyclohexane, as well as mixtures thereof. Preferred hydrocarbons are those boiling in the range from about 100 C. to about 120 C. Still more preferred are the aromatic hydrocarbons and blends thereof such as toluene and mixtures of benzene and xylene. Methyl substituted aromatic hydrocarbons such as toluene and xylene surpress chain-branching reactions and deactivate free radicals, thus decreasing shock sensitivity. For present purposes, toluene is the most satisfactory from the standpoint of both effectiveness and availability.

Furthermore, toluene is inherently difiicult to separate from tetramethyl lead, thereby imparting a fool proof" quality to such concentrates according to the invention.

The proportions of hydrocarbon in the concentrate are critical and lie in the range from about 10 to 150 percent by weight of the tetramethyl lead content as already mentioned. On a volume basis, it is found that suitable concentrates are provided by combining the tetramethyl lead with about 50 percent by volume of hydrocarbon such as toluene. Preferably, the hydrocarbon is present in amounts of at least about 20 to about 50 percent by weight based on the tetramethyl lead content of the concentrate.

The halohydrocarbon scavenger of the concentrate of the invention is preferred, although other types of scavengers containing such elements as hydrogen, carbon, bromine, chlorine, nitrogen and oxygen are suitable. Such scavengers are illustrated by ethylene dibromide, ethylene dichloride, dibromotoluenes, Bfl-dichlorodiethyl ether, 2-chloro-4- nitropentane, etc. With the preferred halohydrocarbon scavengers as exemplified by the bromohydrocarbons and chlorohydrocarbons such as ethylene dibromide and ethylene dichloride, and mixtures thereof, the total amount of scavenger is usually from about 0.5 to about 2.0 theories. A theory is the quantity which reacts with the lead to form lead halide, or more specifically, two atoms of halogen for each atom of lead. Such concentrations are sufiicient to control the amount of deposits due to lead which are formed in the engme.

The concentrate composition of the invention is prepared by simple mixing of the above described ingredients. The components may be put together in any order and mixed by any suitable means, such as circulation with pumps or mechanical stirring or agitation.

Other materials commonly present in gasoline compositions are also suitably incorporated in the concentrate of the invention so long as the essential antiknock characteristics are not afiected. Such additives include dyes, metal deactivators, antiicing agents, rust inhibitors, detergents, ignition control additives and lead extenders.

The examples of the following table illustrate suitable concentrate compositions in accordance with the invention. Unless otherwise specified, the proportions given are on a weight basis.

The explosibility characteristics of various lead antiknock compositions are given in the following table to illustrate the efiectiveness of the concentrates according to the present invention. The compositions are tested by a standard procedure insuring safety and uniform reliability of results. A small sealed glass test tube, having an inside diameter of 8 mm. and containing a regular dynamite blasting cap connected by wires to an electrical source, for initiating explosion, is placed inside another glass tube 6 inches in length and having an outside diameter of 16 mm. The space in the second tube not occupied by the tube containing the blasting cap is filled with 10 ml. of the composition to be tested. The second tube is then sealed and the entire assembly placed inside a lead pipe 7 inches in length having an inside diameter of 18 mm. and an outside diameter of 33.8 mm. After the blasting of the dynamite cap, the maximum average bulge in the diameter of the lead pipe is measured.

TABLE II Lead tube Change Total over pure Test Average diameter tetranumber Composition diameter change ethyl lead 1 None, not exploded 33.8 2. None, no liquid 39. 3 3 ator 43. 3 9. 4. Pure tetraethyl lead 45.2 11.4 5 'Ietruethyl lead, scavenger 45.0 11.2 0.0

mix l5. Puretetramethyllead 50.7 16.9 5.5 7. Tetrarnethyl lead, seav- 48.2 14.4 3.0

anger mix 8 Tetramethyl lead, scav- 45.6 11.5 0.4

engcr mix and toluene EL Picric acid, 1 gram 53.5 19.7 8.3

k e 61.41% tetraethyl lead, 35.68% ethylene dibromide, 2.91% dye and erosene.

" 58.7% tetramethyl lead, 41.3% ethylene dibromide.

" 48.8% tetramethyl lead, 34.6%ethylene dibromide, 16.6% toluene.

From the illustrative test results of the above table, it can be readily seen that tetrarnethyl lead, for some unexplainablereason, is decidedly more explosive and shock sensitive than conventional tetraethyl lead. As a matter of fact, it seems that tetramethyl lead is comparable in explosive characteristics to picric acid which is well known for its high explosive qualities. However, in the form of the improved new antiknock concentrate according to the invention, these dangerous characteristics of tetramethyl lead compared to tetraethyl lead are substantially completely eliminated. Thus it is impossible to use the more effective tetramethyl lead in gasoline manufacture with the same degree of safety as tetraethyl lead.

We claim:

1. An antiknock concentrate comisting essentially of tetramethyl lead, halohydrocarbon scavenger and aromatic hydrocarbon liquid boiling in the range from about C. to about C., the hydrocarbon liquid content of the concentrate being in the range from about 10 to about percent by weight of the tetrarnethyl lead.

2. An antiknock concentrate consisting essentially of tetramethyl lead, haiohydrocarbon scavenger and toluene, the toluene content of the concentrate being in the range from about 10 to about 150 percent by weight of the tetramethyl lead.

3. An antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger, and toluene, the toluene content of the concentrate being above about 10 percent by weight of the tetramethyl lead.

I I! 1.! l i 

2. An antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger and toluene, the toluene content of the concentrate being in the range from about 10 to about 150 percent by weight of the tetramethyl lead.
 3. An antiknock concentrate consisting essentially of tetramethyl lead, halohydrocarbon scavenger, and toluene, the toluene content of the concentrate being above about 10 percent by weight of the tetramethyl lead. 